ANCHORAGE, ALASKA — The attorney for the man charged with killing two co-workers at a Kodiak Island Coast Guard communications facility offered a medical explanation Tuesday for his client’s whereabouts during the shooting.

On his way to work on the morning of the deaths, Curtner said, Wells detected a soft tire on his truck but delayed changing it to spend 20 minutes in a bathroom at the Kodiak airport because of chronic diarrhea.

The timing is crucial.

Federal prosecutors say there’s a 34-minute period between security-camera recordings of Wells’ truck driving toward and away from the Communications Station, giving him time to reach the facility, shoot Richard Belisle, 51, and Petty Officer 1st Class James Hopkins, 41, and return home, where he concocted the flat tire alibi.

Wells is charged with two counts of first-degree murder, two counts of murder of an officer or employee of the United States, and possession of a firearm in a crime of violence. If he is convicted, prosecutors will not seek the death penalty.

U.S. Attorney for Alaska Karen Loeffler said in her opening statement that no other person had the means of escaping detection from security cameras at the Coast Guard Communications Station where the men worked. No robbery or other disturbance took place, she said.

“This murder was personal and intentional,” Loeffler said.

The motive, according to prosecutors, was unhappiness by a disgruntled employee. The Coast Guard was attempting to exert more control over Wells, a nationally recognized antenna technician who for years had called the shots at the shop.

The bodies were found in Building T2, known as the Rigger Shop, an L-shape building about 100 yards from the main facility, Building T1, which is staffed at all hours to monitor messages from mariners.

The morning of the shootings, Belisle’s security card opened the Rigger Shop at 7 a.m. Hopkins’ truck pulled in about 7:08 a.m. Within minutes, they would be dead, Loeffler said.

Belisle was shot in a small office he shared with Wells, Hopkins and supervisor Scott Reckner. Hopkins died in the building’s break room.

Wells’ white pickup truck showed up on security footage passing the main gate of the Coast Guard Air Station two miles away at 6:48 a.m. The same camera recorded the pickup 34 minutes later heading in the opposite direction toward Wells’ home, at 7:22 a.m.

When Wells claimed to have been checking his tire and spending time in a bathroom at commuter airline Servant Air, prosecutors contend he stopped at the airport, switched into his wife’s blue Honda CRV, drove to the Communications Station and shot his co-workers. He was back on the road within five minutes and drove back to the airport, switched to his truck and drove home.

A security camera on Building T1 shows a blurry image of a blue SUV driving by the Rigger Shop at 7:09 a.m. and heading in the opposite direction at 7:14 a.m.

Expert testimony will link the image to the SUV belonging to Wells’ wife, Loeffler said, undercutting Wells’ alibi and revealing his murder plot.

“It was well planned, it was well thought out, but it was not perfect,” she said.

Curtner said the image is not conclusive. The blue blur on which the government case hangs could have been an SUV manufactured by any of nine car companies, he said.

“That’s their identification evidence,” Curtner said.

Prosecutors steadfastly refused to consider other suspects, he said, Investigators should have looked into acquaintances of the victims’ families that had issues with illegal drugs. They instead took their cue from Wells’ Coast Guard supervisor, Scott Reckner, who immediately suggested that Wells had committed the murders.

“He poisoned everybody else to think that,” Curtner said.

Wells is a devoted family man with no criminal record, Curtner said. After serving 20 years in the Navy and Coast Guard, Wells vowed to never again wear a tie or shave and played Santa Claus on occasion with his long beard. The government case is built on a stack of assumptions, he said.

“The facts you will hear will not prove otherwise,” Curtner said. The trial is expected to go three to four weeks.